feat(pgp): Use crypto.py during Egg and Collection verification

[m-horky]

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Complete Description of Additions/Changes:

• Card ID: CCT-131
• Card ID: CCT-405
• Card ID: RHEL-2480
• Card ID: RHEL-2482

This patch adds a self-contained and isolated GPG verification environment. It runs GPG in an isolated environment where only selected PGP keys are allowed to check the file signature matches its file.

GPG creates a directory $HOME/.gnupg/ every time it performs some operation. When run under root, but not manually (e.g. via subscription-manager Cockpit plugin), it tries to create and write to this directory, which pollutes user directories and/or causes SELinux denials.

This patch utilizes the --homedir argument GPG supports in order to move the GPG home directory to a temporary directory for the time of the transaction. After the GPG action is performed, the directory is cleaned up.

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This PR is an improvement over previously reverted https://github.com/RedHatInsights/insights-core/pull/3930